1. Field of the Invention
The present invention relates generally to the manufacture of diethylbenzene, and particularly to a method of making diethylbenzene by reacting ethylbenzene and ethanol over a zeolite catalyst that has been pre-treated by coking the catalyst with an aromatic, an alcohol, or both to increase selectivity.
2. Description of the Related Art
Aromatic conversion reactions are of great industrial interest and importance. Such reactions include alkylation and transalkylation used to produce alkylaromatics, such as ethylbenzene, diethylbenzene, ethyltoluene, cumene and higher aromatics. Dialkylbenzenes, such as xylene and diethylbenzene, are of particular importance, as they are used for the production of polyesters, solvents, photodevelopers and antioxidants. Diethylbenzene, in particular, is an important raw material for conversion divinyl benzene monomer, and is also used in refineries for the separation of close boiling isomers. Diethylbenzenes are also used as solvents and precursors for cross-linking agents in producing resins.
A wide variety of reactor systems have been developed for carrying out aromatic conversion reactions. Conventional aromatic conversion systems include fixed bed reactors, such as multi-tubular fixed bed reactors, and fluidized bed reactors. The alkylation of ethylbenzene with ethanol is a reaction that is of immense industrial importance. This reaction provides an alternate route for producing various isomers of diethylbenzene (ortho-, meta- and para-diethylbenzene). Due to the rapid development of biochemical engineering technology, the cost of obtaining ethanol has greatly decreased. Thus, the direct use of ethanol in manufacturing diethylbenzene is of economic benefit to those countries where biomass-derived alcohol is readily available for manufacturing chemicals. Additionally, in situ dehydration of alcohols leads to prolonged catalyst activity, since the water of reaction suppresses coke formation, which is in contrast to vapor phase alkylation with ethylene at higher temperatures, where significant coke formation typically occurs.
Alkylation of ethylbenzene to diethylbenzene is commonly performed as an acid-catalyzed process. Diethylbenzene is conventionally synthesized by using existing alkylation catalysts, such as AlCl3, HF, BF3, and the like. Due to the strong acidity of these catalysts, disposal of the selected catalyst causes serious environmental pollution, along with corrosion of equipment used during the manufacturing process.
Thus, a method of making diethylbenzene solving the aforementioned problems is desired.